Method of making an aerosol container

ABSTRACT

An aerosol container includes a main body portion that is constructed and arranged to withstand aerosol pressurization within a range that is about 90-180 prig and a threaded finish portion that is unitary with the main body portion. The threaded finish portion has at least one helical thread, a support ledge beneath the helical thread and a secondary flange that is positioned beneath the support ledge. The secondary flange has an outer circumference that is noncircular in at least one location, whereby it may be engaged during a capping operation to prevent rotation of the container during capping. A method of making an aerosol container in which a preform is capped before the blow molding process is also disclosed.

BACKGROUND OF THE INVENTION 1. Field of the Invention

This invention relates broadly to the field of containers that areadapted to hold highly pressurized contents, such as aerosol mixtures,and more particularly to a blow molded plastic aerosol container havinga finish portion that is constructed and arranged to provide maximumresistance to deformation and stress cracking at high internalpressures.

2. Description of the Related Technology

Aerosol containers have conventionally been fabricated from metal, andare conventionally formed as a cylindrical tube having upper and lowerend closures. The bottom end closure is typically shaped as a concavedome, and the upper end closure typically includes a manually actuatablevalve for dispensing the pressurized aerosol contents of the container.

Metallic containers have certain inherent disadvantages, such as atendency to rust over time and to scratch surfaces with which they maycome into contact.

Efforts have been made in the past to develop plastic aerosolcontainers, but have encountered difficulties, mainly relating tocontrolling the deformation of the plastic material as a result of thesignificant internal pressurization that is necessary in an aerosolcontainer. Aerosol containers commonly require internal pressures of themagnitude of 50-300 psi, which is significantly greater than pressuresthat are typically encountered in other packaging applications for whichplastic material has been used, such as the packaging of carbonatedbeverages. Accordingly, design considerations for plastic aerosolcontainers are quite different than they are for lower pressurepackaging applications such as plastic beverage containers.

One common type of plastic container is fabricated from a material suchas polyethylene terephthalate (PET) and is manufactured from aninjection molded preform having a threaded finish portion using thereheat stretch blow molding process. While such containers hold somepromise for aerosol applications, they are susceptible to stresscracking in the finish portion while under pressurization. In addition,the finish portion of such containers has a tendency to deform when thecontainer is pressurized, possibly resulting in a loss of sealingintegrity between the container and the aerosol dispensing closure.

A plastic aerosol container that utilizes a threaded finish portion alsorequires application of an aerosol dispensing closure to the finishportion at a torque that may be greater than that used for theapplication of closures to conventional, non-aerosol containers.Conventional capping machines may be unable to generate such torquewithout causing undesired rotation of the container.

A need exists for an improved blow molded plastic aerosol container thatis less susceptible to stress cracking and deformation in the finishregion than are conventional blow molded containers. A need also existsfor a plastic aerosol container that can have an aerosol dispensingclosure applied thereto at higher torques without rotation of thecontainer.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to provide an improvedblow molded plastic aerosol container that is less susceptible to stresscracking and deformation in the finish region than are conventional blowmolded containers.

It is further an object of the invention to provide a plastic aerosolcontainer that can have an aerosol dispensing closure applied thereto athigher torques without rotation of the container.

In order to achieve the above and other objects of the invention, anaerosol container according to a first aspect of the invention includesa main body portion containing an aerosol mixture having an aerosolpropellant. The container further includes a threaded finish portionthat is unitary with the main body portion. The threaded finish portionhas at least one helical thread, a support ledge beneath the helicalthread and a secondary flange that is positioned beneath the supportledge. The secondary flange has an outer circumference that isnoncircular in at least one location, whereby it may be engaged during acapping operation to prevent rotation of the container during capping.

A method of assembling an aerosol container according to a second aspectof the invention includes steps of providing a container having athreaded finish portion, a support ledge positioned beneath the threadedfinish portion and a secondary flange positioned beneath the supportledge. The secondary flange has at least one noncircular portion. Amethod further includes a step of preventing rotation of the containerby engaging the noncircular portion of the secondary flange, andscrewing at least a portion of an aerosol dispensing closure assemblyonto the threaded finish portion at a torque that is within a range ofabout 15 in-lbs to about 50 in-lbs. The container is then pressurizedwith an aerosol mixture having an aerosol propellant.

A method of making an aerosol container according to a third aspect ofthe invention includes steps of providing a preform having a threadedfinish portion, a support ledge positioned beneath the threaded finishportion and a secondary flange positioned beneath the support ledge, thesecondary flange having at least one noncircular portion; preventingrotation of the preform by engaging the noncircular portion of thesecondary flange; screwing at least a portion of an aerosol dispensingclosure assembly onto the threaded finish portion of the preform; andblow molding an aerosol container from the preform.

These and various other advantages and features of novelty thatcharacterize the invention are pointed out with particularity in theclaims annexed hereto and forming a part hereof. However, for a betterunderstanding of the invention, its advantages, and the objects obtainedby its use, reference should be made to the drawings which form afurther part hereof, and to the accompanying descriptive matter, inwhich there is illustrated and described a preferred embodiment of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary cross-sectional view taken along lines 1-1 inFIG. 2;

FIG. 2 is a top plan view of an aerosol container assembly that isconstructed according to a preferred embodiment of the invention;

FIG. 3 is a bottom plan view of the aerosol container assembly that isshown in FIG. 2;

FIG. 4 is a side elevational view of the finish portion of the aerosolcontainer assembly that is shown in FIG. 2;

FIG. 5 is a cross-sectional view taken along lines 5-5 in FIG. 3;

FIG. 6 is a cross-sectional view taken along lines 6-6 in FIG. 3;

FIG. 7 is a diagrammatical view depicting the manufacture of an aerosolcontainer according to an alternative embodiment of the invention;

FIG. 8 is a diagrammatical view depicting an aerosol closure assemblyaccording to the preferred embodiment of the invention;

FIG. 9 is a cross-sectional view taken through a preform that isconstructed according to the preferred embodiment of the invention;

FIG. 10 is a flowchart depicting a method according to the preferredembodiment of the invention; and

FIG. 11 is a flowchart depicting a method according to an alternativeembodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring now to the drawings, wherein like reference numerals designatecorresponding structure throughout the views, and referring inparticular to FIG. 1, an aerosol container assembly that is constructedaccording to a preferred embodiment of the invention includes a plasticaerosol container 10 having a main body portion 12 that is constructedand arranged to withstand aerosol pressurization within a range of about50 psig to about 300 psig. More preferably, the main body portion 12 isconstructed and arranged to withstand aerosol pressurization within arange of about 90 psig to about 180 psig.

Plastic aerosol container 10 is preferably fabricated from a plasticmaterial such as polyethylene terephthalate (PET), polyethylenenaphthalate (PEN), acrilonitrile (AN), polycarbonate (PC), polyamide(Nylon), or a blend containing some combination of the same from aplastic preform using a conventional blow molding process such as thereheat stretch blow molding process. In the preferred embodiment,container 10 is fabricated from a high intrinsic viscosity polyethyleneterephthalate material, which most preferably has an intrinsic viscositythat is substantially within a range of about 0.76 to about 0.95.

Container 10 preferably has an average wall thickness in the main bodyportion 12 that is substantially within a range of about 0.018 inch toabout 0.022 inch, permitting it to withstand aerosol pressures.

The aerosol container 10 further includes a threaded finish portion 14that is unitary with the main body portion 12 and that has at least onehelical thread 16 defined thereon for receiving an aerosol dispensingclosure. Finish portion 14 further includes a support ledge 18 beneaththe helical thread 16, which is used to help convey the container 10during manufacture and filling. The support ledge 18 has a first maximumouter diameter D_(L), as is best shown in FIG. 1.

The support ledge 18 is preferably constructed so that it has asubstantially circular circumference as viewed in top plan. In thepreferred embodiment, the outer circumference of the support ledge 18includes a pair of small recesses 24, which are used for registering theposition of the container 10 during the capping process, in which anaerosol dispensing closure is applied to the finish portion 14.

The threaded finish portion 14 further includes at least one secondaryflange 20, which is positioned beneath the support ledge 18. Thesecondary flange 20 is preferably constructed so that it has an outercircumference that is noncircular in at least one location, so that itmay be engaged during a capping operation to prevent rotation of thecontainer 10 during capping.

The secondary flange 20 in the preferred embodiment is fabricated usingan injection molding process together with the rest of a plastic preform50, shown in FIG. 9, which is used to manufacture the aerosol container10 using a reheat stretch blow molding process. The plastic preform 50includes a body portion 52.

In an alternative embodiment of the invention, shown in FIG. 7, a blowmolded aerosol container 30 includes a threaded finish portion 32 havinga support ledge 34 and a secondary flange 36. In this embodiment, thesecondary flange 36 is fabricated during the blow molding processthrough the use of a mold 38, and is not part of the preform that isused to manufacture the container 30.

In another alternative embodiment of the invention, anti-rotationfeatures could be incorporated into the support ledge of the finishportion without the provision of a secondary flange. For example, thesupport ledge could be provided with two or more flat surfaces, groovesor notches on the underside of the support ledge or one or more lugs ornotches on the top surface of the support ledge.

The secondary flange 20 is preferably constructed so as to have a secondmaximum outer diameter D_(S), which is not substantially greater thanthe first maximum outer diameter D_(L) of the support ledge 18.Preferably, the second maximum outer diameter D_(S) of the secondaryflange 20 is substantially the same as the first maximum outer diameterD₁ of the support ledge 18.

Preferably, the secondary flange 20 has at least one substantially flatportion defined thereon that may be engaged by a capping machine inorder to prevent relative rotation of the container 10 with respect tothe capping machine during the capping process. As is best shown in FIG.3, the secondary flange 20 preferably has four flat portions 22 that areevenly spaced around the circumference of the secondary flange 20.

An annular space 28 is defined between the support ledge 18 and thesecondary flange 20. Annular space 28 has a minimum vertical dimensionH_(S) that is preferably at least about 1 mm, and that is morepreferably at least about 1.5 mm.

The aerosol container assembly further includes an aerosol dispensingclosure assembly 40, which is diagrammatically shown in FIG. 8. Theaerosol dispensing closure assembly 40 includes an apron or collar 42that is adapted to be threaded onto and sealed to the threaded finishportion 14. Securing structure is preferably provided in order toprevent the consumer from unscrewing the aerosol dispensing closureassembly 40 from the container 10, which in the preferred embodiment isa glue that is applied to collar 42 of the aerosol dispensing closureassembly 40 and the finish portion 14.

The aerosol dispensing closure assembly 40 also preferably includes ametallic insert 44 mounted on the collar 42 having a central opening inwhich an aerosol dispensing valve 46 is positioned.

A method of assembling an aerosol container assembly according to thepreferred embodiment of the invention is diagrammatically shown in FIG.10 and includes providing a container 10 as described above having athreaded finish portion 14, a support ledge 18 positioned beneath thethreaded finish portion and a secondary flange 20 positioned beneath thesupport ledge 18. The secondary flange 20 preferably has at least onenoncircular portion.

The collar 42 of the aerosol dispensing closure assembly 40 is thenscrewed onto the threaded finish portion 14 using a commercial cappingmachine. During the capping process, the container 10 is secured againstrotation relative to the capping machine by engagement of a portion ofthe capping machine with the noncircular portion of the secondary flange20. The collar 42 of the aerosol dispensing closure 40 is preferablyscrewed onto the threaded finish portion at a torque that issubstantially within a range of about 15 in-lbs to about 50 in-lbs. Thecontainer 10 is then filled with product, after which the metallicinsert 44 of the aerosol dispensing closure assembly 40 is applied tothe collar and the container is pressurized with an aerosol mixture at arange of pressurization that is substantially between about 50 psig toabout 300 psig, and more preferably substantially within a range ofabout 90 psig to about 180 psig using known aerosol pressurizationprocesses and equipment.

The aerosol mixture preferably includes a propellant, which could be aliquefied gas propellant or a compressed or soluble gas propellant.Liquefied gas propellants that could be used include hydrocarbonpropellants such as propane, isobutene, normal butane, isopentane,normal pentane and dimethyl ether, and hydrofluorocarbon propellantssuch as difluoroethane (HFC-152a) and tetrafluoroethane (HFC-134a).Compressed and soluble gas propellants that could be used include carbondioxide (C02), nitrous oxide (N20), nitrogen (N2) and compressed air.

In an alternative embodiment that is depicted in FIG. 11, the collar 42of the aerosol dispensing closure assembly 40 could be secured to thethreaded finish portion 14 of the preform 50 prior to blow molding thecontainer 10 and its main body portion 12. Securing structure ispreferably provided in order to prevent the consumer from unscrewing theaerosol dispensing closure assembly 40 from the container 10, which inthe preferred embodiment is a glue that is applied to the collar 42 andthe finish portion 14.

During this preform capping process, the preform 50 is secured againstrotation relative to the capping machine by engagement of a portion ofthe capping machine with the noncircular portion of the secondary flange20, shown in FIG. 9. The collar 42 is preferably screwed onto thethreaded finish portion 14 of the preform 50 at a torque that issubstantially within a range of about 15 in-lbs to about 50 in-lbs.

The container 10 is then blow molded and filled with product, includingthe aerosol mixture. The container 10 is subsequently pressurized.

It is to be understood, however, that even though numerouscharacteristics and advantages of the present invention have been setforth in the foregoing description, together with details of thestructure and function of the invention, the disclosure is illustrativeonly, and changes may be made in detail, especially in matters of shape,size and arrangement of parts within the principles of the invention tothe full extent indicated by the broad general meaning of the terms inwhich the appended claims are expressed.

1. A method of assembling an aerosol container, comprising: providing acontainer having a threaded finish portion having at least one helicalthread, a support ledge positioned beneath the threaded finish portion,the support ledge having at least one position-registering recessdefined therein, and a secondary flange positioned beneath the supportledge, the secondary flange having an outer circumference that isnoncircular in at least one location; preventing rotation of thecontainer by engaging the noncircular portion of the secondary flange;screwing at least a portion of an aerosol dispensing closure assemblyonto the threaded finish portion at a torque that is within a range ofabout 15 in-lbs to about 50 in-lbs; and pressurizing the container withan aerosol mixture having an aerosol propellant.
 2. The method accordingto claim 1, wherein the support ledge has a first maximum outer diameterand the secondary flange has a second maximum outer diameter, andwherein the second maximum outer diameter is substantially the same asthe first maximum outer diameter.
 3. The method according to claim 1,wherein the support ledge has a first maximum outer diameter and thesecondary flange is a second maximum outer diameter, and wherein thesecond maximum outer diameter is not substantially greater than thefirst maximum outer diameter.
 4. The method according to claim 1,wherein the secondary flange has at least one substantially flat portiondefined thereon.
 5. The method according to claim 1, further comprisingsecuring the aerosol dispensing closure against rotation with respect tothe container by applying a securement means.
 6. The method according toclaim 1, wherein the threaded finish portion and the main body portionare fabricated from a material comprising polyethylene terephthalate. 7.The method according to claim 1, wherein a space is defined between thesupport ledge and the secondary flange, and the space has a minimumvertical dimension that is at least about 1 mm.
 8. The method accordingto claim 7, wherein the minimum vertical dimension is at least about 1.5mm.